Emit test-balls:record on the shared pi.events bus after the session-start
make test run completes, so test-balls shows a ball for it like any other run.
The run is now fire-and-forget: session start no longer blocks on make test,
and the emit always lands after every extension's session_start handler has
run (project extensions load before global ones, so emitting synchronously
raced test-balls' runs reset). Exactly one ball is recorded per run, even if
UI reporting fails.